Screen for rontgen-ray examination



June 16, 1925.

AI o. AKERLuND l ,SCRBN ,FOR RNTGEN RAY EXAMINATION ,mnd Dec. 2v, 1922 Patented June 16, 1925i.

AKH onor REEL-UND, or STOCKHOLM,` SWEDEN.

SCREEN non fnNTenN-RAY nxmvrINArroN.` 1

Application ledvDecember 27, 1922. Serial No. 609,299.

To all whom itmag/ concern.'

Be it known that I, nn OLoF KERLUND, a subject of the King of Sweden, residing at Kungsholms Hamnplan 3, Stockholm, Sweden, have invented certain new and useful Improvements in Screens for Rntgen- Ray Examination, of which the following is a specification.`

For the examining of Subjects by means of Rntgen-rays it is necessary to'shutout the so called secondary VRntgen-rays in order to gain a clear image. 'For the said purpose screens are used, located between the subject to be examined and the photographic or iiuoroscopic plate. screens generally consist of a plate made from a material permeable for the Rntgenrays and provided with strips of laminee of a material such as lead, which is opaq'ue to the rays, the said strips being located in the permeable material and positioned in the direction of the primary rays in order not to obstruct the passage of the same. During the photographing operation the screen is moved slowly perpendicularly to the strips, so that the secondary rays, which otherwise contribute to rendering the image foggy, are partially shut out, without the strips, owing to the movement of the screen, effecting any shadows on the plate. It evident, however, that secondary rays, which are substantially parallel to the longitudinal direction of the Strips, are not shut out by the said arrangement. For removing the drawback just mentioned improvements have been proposed, the result of which, however, is not good owing to the fact that they are based upon a wrong principle in some or other respect. According to the said improvements the screens are provided with strips extending in different directions and thus crossing each, which results in the intersections of the strips, during the rotary motion generally imparted to the screen, effecting substantially ring-shaped images on the plate.

In order to gain a perfect picture from the body to be examined the screen, according to this invention, is provided with two or more spiral strips of metal or any other impermeable material provided in a carrier of suit-able material and extending from the same centre parallel to each other.

A screen arranged in accordance with this invention is shown as an example in The said the accompanying drawing. Fig. 1 is an elevation of the screen and Fig.: 2 shows a cross sectionof the same.

`1 is a disk of a permeable material, such as wood. In a pluralityof spiral grooves .cut inthe disk l strips 2 of animpermeable material such as lead are located. The grooves and consequently the spiral strips 2 vcoincide in direction with that of primary Rntgen-rays 3 emanating from a Rntgentube, as illustrated `in Fig. 2. The disk which is enclosedby a metal ring l and carried by balls 5, running in a frame 6, is rotated by means of a toothed wheel 7 mesh- Y ing with teeth 8 provided on the disk 1. The apparatus is covered by a plate 9 of aluminium or the like.

In order now to gain a uniform screening of the secondary Rntgen-rays from the centre of the disk to the periphery of the same all the spiral strips 2 extend from the centre of the disk, forming the same angles with each other, to the periphery of the disk parallel to each other, so that tangents to the strips at their intersections with the same arbitrary radius are parallel. The strips are located at the same distance from each other and the distance between the coils of each spiral strip is invariable from the centre of the disk to the periphery of i the same. Preferably, the inner ends of the strips l are thinned to such a degree is possible by technical means, so that all strips may extend as near the centre of the disk as possible and no part of the disk may be 'unscreened During the photographing operation the disk l is rotated, so that the effecting of images of the strips is prevented.

The provision of a plurality of spiral strips arranged as stated above involves the advantage of the secondary rays in all directions being shut out, especially good Rntgen-pictures being thereby gained. As the coils of the strips arelocated at the same dist-ances'from each other, the rays passing through the screen are uniformly impaired throughout the pla-te. so that the latter is uniformly lighted. Owing to the fact that the strips are Spiral and do not intersect and no radial strips are provided, Shadowless pictures will be effected. In consequence of a plurality of strips located close to each other and extending from the same centre being used, the pitch of each spiral4 strip may be great without the efficiency of the scieen-being @redit-Iced. Be5ides,; the f great pitch involvesthe advantage 'of each spiral strip greatly diverging from the circular strips 'of an vinpernieahle material, allweX- tending from the same centre and having their planes coinciding in `direction-with 3that of the, primary Rntgen-rays.

2.1 ln a vrotatable Screenv for Rntgen-ray exaiiiiiiationthe combination of a disk of a rmaterial permeable forythe rays4 andr a plu- 20 ra'lity olf parallel spiral 'strips of an impermeable material, Ywhich all extend -i'nthe Satine @entre -aaid-theGeile (if-Which are l0- Cated at the same distance from Ieach other,

'the said Strips having their planes eoineid n igfangdireetienf,withthat ot the primary Rntgen-rays.

fi-3.3111 ajnotatalilecreen for Rntgen-ray examination the combination 0l' a disk 0l? a .materialpermeablefor the rayS, and a pllirality of parallel Spiral Strips of an impermeable 1naterial,..vtall extending :iiaonii the sainev'oentreand having' their .planes coincidingHiir direetion.'v with ,that et thepixmiary Kl;''iiitgenTrays, .tlie,.inner.\ ends of. `the said ,stripsabeingthinned.

ln testimony-n lliereof Lhavealiiied my ieigirataiifein presence. oi' tivo witnesses.

fKE .OLoF-.KEBLUND 'Vitnesses Rennen APELGREN, LLVIBERGy V 

